Piezo-electric device



April 2, 1935. l. F BYRNES El' AL 1,996,569

I PIEzo ELECTRIC DEVICE Filed Nov. 16, 1929 /zo F191. f/F ,/7\ J2 /4 C CC C w y C ze Figa..

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l Patented Apr. 2, 1935 UNITED STATES PATENT OFFICE PIEZO-ELECTRICDEVICE Irving F. Byrnes and Harry R. Meahl, Schenectady, N. Y.,assignors to General Electric Company, a corporation of New YorkApplication November 16, 1929, Serial No. 407,785

2 Claims. (Cl. 219-19) Our invention relates to piezo-electric devicescrystal I! through the leads 20 and 2|, which are such as are used tocontrol the operating freconnected respectively to an electrode 22 andan quency of oscillation generators. It has for its electrode 23 whichforms the bottom of the cell. principal object the provision of animproved de- A thermometer 24 may be provided for observavice of thischaracter which operates at a fretion of the cell temperature. It willof course be quency substantially independent of ambient apparent thatthe upper electrode 22 and the temperature. lower electrode 23 areelectrically insulated from It is well known that a piezo-electriccrystal one another by any suitable means. The illussuch as a slab ofquartz or the like tends to vibrate trated type of crystal mounting iswell known and at a frequency dependent on its mechanical need not bedescribed in further detail. 10 dimensions when it is subjected to anelectrical In 3 the crystal C611 iS indicated at 25 by field. It is alsoknown that the natural vibration dotted lines, and the 'thermo-regulatorI6, the period of the crystal is dependent to some extent crystal I9,and the heater or heating layer I2 on the temperature to which it issubjected durare shown diagrammatically as enclosed within ing itsoperation, and various means have been the cell. Heating current issupplied to the heatprovided in the past for regulating the temperainglayer I2 from any suitable source such for ture of the crystal. Ourinvention relates to an example as an alternating current source 25improved apparatus whereby changes in the temthrough a relay 21. Therelay 21 is provided with perature of the crystal are minimized to adegree an operating coil 2l which is connected in the not heretoforerealized. plate circuit of an electron discharge device 29, 20

Our invention will be better understood from through which the supply ofcurrent to the heatthe following description when considered in coninglayer is controlled. nection with the accompanying drawing, and its Itwill be observed that the electron discharge scope will be pointed outin the appended claims. device 29 includes a cathode 30, a control grid3 I,

Referring to the drawing, Figs. 1 and 2 are and an anode or plate 32.Heating current is 25 vertical and horizontal sectional views of a piezosupplied from the source 26 to the cathode 30 electric cell wherein ourinvention has been emthrough a transformer 33.v Plate and gridconbodied, and Fig. 3 is a wiring diagram of the control potentials areapplied to the device 29 through trol circuits through which temperaturecontrol a transformer 34, the plate circuit of the device 30 of thecrystaliseffected. 2! being connected across one section of the 30 Asindicated by Figs. 1 and 2, the cell comprises secondary circuit of thetransformer 34 and the an outer protective layer I0 which may be of grid3| being connectedtothe cathode 30 through basswood or the like, aninsulation layer Il which a capacitor and another section of the may beany suitable material, a heating layer I2, secondary circuit of thetransformer 34. A

35 a heat distributing layer I3, a heat attenuating smoothing capacitor3S is connected in shunt to 35 layer I4, and a heat storing layer I5.The heat the operating coil 28 of the relay 21, and a reattenuatinglayer, which is shown as an enclosed sistor 31 is connected between thethermo-reguair space may include a layer of hair felt or other lator 46and the grid 3l. The operation of the suitable material, and is arrangedto enclose a device will be readily understood without detailedthermo-regulator I6 of any suitable type. The explanation. Assuming thatthe temperature of 40 heat distributing layer comprises any suitable thecell increases above the desired value, the material having high heatconductivity and low mercury within the thermo-regulator I6 expands heatstorage capacity. The thermo-regulator I6 and a connection is completedbetween the termiis preferably mounted near theheat distributing nalsI1, thus connecting the grid 3i directly to layer I3, and in theillustrated embodiment of the the cathode 3l, through resistor 31 whichlimits 45 invention is a mercury contact device provided current throughcontacts I1 permitting the transwith a pair of terminals I1 which, ashereinafter mission of current through the device 29 to the explained,are arrangedto control the grid potenoperating coil 28 of the relay 21,which is opertial of a vacuum tube device through which the ated to itsupper or open position, interrupting supply of heating current to theheating layer I2 the supply of heating current to the heating 50 iscontrolled. This heating current is supplied layer I2. When thetemperature of the device through leads I8. The piezo-electric crystalis decreases below the desired value the mercury indicated at I9 andisenclosed within the heat within the thermo-regulator Il contracts, thestoring layer I5, which is preferably made of circuit between theterminals I1 is interrupted,

copper. Electric potential is applied to the and thegrid 3|,whichisconnected to the cathode 55 3@ through the capacitor in the left-handsection of the secondary circuit oi the troer 3d, is subjected to apotential which interrupts or reduces the current of the device 2@ andpermits the relay 2l to move to its lower or closed position, thusconnecting the heating layer i@ to the source 26.

It has been found in the operation of the device that the range oftemperature variation of the crystal is dependent on several factors notheretofore well mi Br smug, the range of temperature variation of thecrystal depends on the sensitivity oi the thermo-regulator and on thesize of the heater. ln the operation of the device it has been foundthat the heat distributing layer i8 is of great importance. It has alsobeen found that the .best results are secured when the thermo-regulatoris mounted inproximity to the heating layer whereby it is sensitivelyresponsive to heat produced thereby, and is suciently removed from the`Wall i5 to permit the latter to act as a relatively constanttemperature heat reservoir, or balance wheel. Ii the thermo-regulator ismounted betvveen the insulation layer ii and the hting layer i2, forexample, a change of about 1 C. is found to exist for each 8 C. changein room temperature. When the hwt distributing layer i@ is provided andthe thermo-regulator is mounted in proximity to this layer, it rf i..been found that the range of variation in the crystal temperature isabout 111; of 1 for each 20 C. change in room temperature. The heatdistributing layer and the proper location of the thermo-regulator aretherefore important considerations in the construction oi the type ofcrystal cell herein described.

The large heat storing mass of the base plate 28 and Walls i5 aiords arelatively co f m temperature reservoir of heat, or heat mi :n ce wheel,thereby very greatly reducing temperature variations Within theseoperation of the cl a considerable cunt of heat is dissipated in thecrystal due to its operation. Since the crystal is in intimate heatconducting relation with the base 23 and walls i5 this heat is quicklyabsorbed in the reservoir without produling large temperature variationin the c asi ce wir we cl as new and d m secune by Letters Patent oi'the United Sta, is,-

incasso l. The combination, in a temperature control device forpiezo-electric crystals, of a chber having a wall ci high heatconductivity and low heat storing capactiy, a heating winding woundabout the exterior surface oi said wall thereby evenly to distributeheat over said surface, an inner chamber enclosed by and spaced fromsaid walls, said inner chamber having massive Walls of high heat retgcapacity, one of said massive walls being in intimate heat conductingrelation with the crystal and a temperature responsive means forcontrolling said heating ding, said temperature responsive means beinglocated in suiiciently close heat conducting relation with said heatingwinding to produce sensitive response to temperature variations producedthereby and sumciently removed from saidI massive wall to permit thelatter to act as a relatively constant tem'perature heat reservoirthereby to protect the crystal from heat variations produced by saidheating means.

2. The combination, in a temperature control device for piezo electriccrystals, a housing for said crystal having thick massive walls of highheat storing capacity, one of said walls being of greater thickness andmass than the others, the piezo electric crystal being mounted inintimate heat conducting relation with said wall of greater thicknessand mass whereby heat dissipated in the crystal is quickly absorbed insaid walls, a heat attenuating chamber enclosing said housing, the wallsthereof being spaced from the Walls of said housing and having high heatconductivity and low heat storing capacity, a heating winding wound uponthe exterior surface of said attenuating cber thereby evenly todistribute heat about said crystal, and temperature responsive means tocontrol said said means being located in suiciently close heatconducting relation with said heating winding to produce sensitiveresponse to temperature variations produced thereby and suiiicientlyremoved from said housing to permit said housing to act as a relativelyconstant temperature heat reservoir to protect the crystal fromtemperature varlations produced by said heating winding.

